The present invention relates to a fly-back transformer for use in the supply of a DC high voltage into a cathode-ray tube such as TV image receiving machine or the like, and more particularly, to a fly-back transformer, which is adapted to reduce higher harmonic ringing to be caused in the secondary winding during the scanning period of a horizontal deflecting circuit.
As to a general construction of conventional fly-back transformer, FIG. 1 is an electric circuit diagram of a high-tension output circuit having a flay-back transformer connected with the horizontal deflecting circuit. A horizontal output transistor 1, a damper diode 2, a resonance capacitor 3, a horizontal deflecting coil 4, and an S-shape correcting capacitor 5 are disposed in the electronic circuit diagram. A fly-back transformer 6 has a primary winding 61 and a plurality of secondary windings 62, 63, 64 and 65 therein. Diodes 71, 72, 73 and 74 are alternately connected with the secondary windings. A high tension output terminal 81 and an earth terminal 82 are disposed in the fly-back transformer.
Normally, such a fly-back transformer 6 as described hereinabove has the primary-winding-wound low-tension bobbin engaged with a closed magnetic path core composed of a pair of -shaped cores butted, further has a split type high-tension bobbin engaged therewith, the split type high-tension bobbin having many grooves with a plurality of secondary windings 62, 63, 64 and 65 alternately connected to the diodes 71, 72, 73 and 74 being wound into them. These windings are accommodated within an insulated case and are resin-molded.
A shot-pulse 9 is caused during a fly-back period of a horizontal deflecting circuit, as shown in FIG. 2, in the secondary windings of the fly-back transformer constructed as described hereinabove, and the ringing 10 is caused during the scanning period. As the ringing 10 during this scanning period deteriorates the picture quality by vertical stripes caused on the TV picture face of, for example, a TV image receiving machine, it is required to be made as little as possible. The ringing 10 is caused by a series resonance circuit made by the leakage inductance and the distributed capacity with respect to the primary winding 61 of the secondary windings 62, 63, 64 and 65. Although the fly-back transformer is desired to be constructed to reduce the leakage inductance and the distributed capacity in order to make such ringing 10 smaller to prevent the picture-quality deterioration, there is a restriction point to such construction as described hereinabove. Accordingly, the electric characteristics was conventionally improved through the so-called high harmonic tuning of tuning the series resonance circuit of the leakage inductance and the distributed capacity with respect to the primary of the secondary windings to the odd times of the basic pulse frequency to be inputted to the primary winding.
However, even if such an improvement measure was taken, the improvement in the electric characteristics of the picture-quality deterioration was restricted.